TWI850161B - Multilayer piezoelectric device and microelectromechanical speakers applying the same - Google Patents

Abstract

A multilayer piezoelectric device includes a semiconductor substrate, a multilayer piezoelectric structure, a first connecting electrode and a second connecting electrode. The multilayer piezoelectric structure includes a plurality of piezoelectric multilayer films stacked in sequence. Each piezoelectric multilayer film includes a first electrode layer, a first piezoelectric layer, a second electrode layer, and a second piezoelectric layer. The first electrode layer and the second electrode layer respectively include a first connecting pattern and a second connecting pattern, and vertical projections of the first feed pattern and the second feed pattern do not overlap. The multilayer piezoelectric structure includes a first opening and a second opening exposing parts of the first feed pattern and the second feed pattern of each piezoelectric multilayer film, respectively. The first connection electrode and the second connection electrode are respectively in the first opening and the second opening, and connecting the first electrode layer and the second electrode layer.

Description

Multilayer piezoelectric element and micro-electromechanical speaker using the same

The present disclosure relates to the field of piezoelectric materials, and in particular to a multilayer piezoelectric element and a micro-electromechanical speaker using the same.

Today's technology can miniaturize many components through semiconductor manufacturing processes. Piezoelectric components are currently made using semiconductor technology and can be used in sensors, micro-electromechanical speakers, etc. They can sense tiny vibrations and convert them into electrical signals.

However, compared to piezoelectric components made of traditional bulk materials, the current piezoelectric components made with semiconductor technology use a stepped structure to expose part of the positive and negative electrodes, but this also limits the thickness of the overall stacking. However, due to the thickness limit, it is difficult to increase the driving voltage, and the use is relatively limited, especially when used in speakers, the sound pressure gain, especially the high-frequency audio performance is poor.

Here, the present disclosure provides a laminated piezoelectric device. In some embodiments, the laminated piezoelectric device includes a semiconductor substrate, a laminated piezoelectric structure, a first connecting electrode, and a second connecting electrode. The laminated piezoelectric structure is located on the semiconductor substrate and includes a plurality of piezoelectric laminated films. Each piezoelectric laminated film is stacked in sequence, and each piezoelectric laminated film includes a first electrode layer, a first piezoelectric layer, a second electrode layer, and a second piezoelectric layer in sequence from bottom to top.

The first electrode layer includes a first electrode circuit pattern and a first connection pattern, and the first connection pattern is connected to the first electrode circuit pattern. The first piezoelectric layer covers the first electrode layer. The second electrode layer is located on the first piezoelectric layer and includes a second electrode pattern and a second connection pattern, and the second connection pattern is connected to the second electrode pattern. The second piezoelectric layer covers the second electrode layer. The first electrode layer of the lowermost piezoelectric stacked layer film is located on the semiconductor substrate, and the first electrode layers of the remaining piezoelectric stacked layer films are located on the second piezoelectric layer. The vertical projections of the first connection pattern of the piezoelectric laminated film overlap each other, the vertical projections of the second connection pattern overlap each other, and the vertical projections of the first connection pattern and the second connection pattern do not overlap at all. The laminated piezoelectric structure includes a first opening and a second opening, and the first opening and the second opening respectively expose a portion of the first connection pattern of each piezoelectric laminated film and a portion of the second connection pattern of each piezoelectric laminated film.

The first connecting electrode is located in the first opening, connected to each first electrode layer, and connected to each first electrode layer in parallel. The second connecting electrode is located in the second opening, connected to each second electrode layer, and connected to each second electrode layer in parallel.

In some embodiments, the areas of the piezoelectric layers are the same.

In some embodiments, the number of the piezoelectric stacked films is greater than five. More preferably, in some embodiments, the number of the piezoelectric stacked films is greater than eight.

In some embodiments, the first piezoelectric layer and the second piezoelectric layer are selected from the group consisting of lead zirconate titanate (Pb(ZrTi)O ₃ , PZT), barium titanate (BaTiO ₃ ), lead titanate (PbTiO ₃ ) and aluminum nitride (AlN).

In some embodiments, the semiconductor substrate is a silicon substrate. Furthermore, a silicon dioxide layer is included between the silicon substrate and the laminated piezoelectric structure.

In some embodiments, the first electrode layer and the second electrode layer are a group consisting of platinum, copper, and aluminum.

Furthermore, a titanium (Ti) layer is included between the first electrode layer of the bottom one of the piezoelectric stacked layers and the semiconductor substrate.

Here, a micro-electromechanical piezoelectric loudspeaker is also provided. In some embodiments, the micro-electromechanical piezoelectric loudspeaker includes the multilayer piezoelectric element described in the above embodiments.

As shown in the above embodiments, by designing the first connection pattern and the second connection pattern on different sides, the first connection patterns are connected to each other through the first connection electrode and the second connection patterns are connected to each other through the second connection electrode on the side by drilling technology. In this way, it is not necessary to reserve electrode openings when stacking layers, and the effect of multi-layer stacking can be achieved, and when used as a micro-electromechanical speaker, it can have a better performance in sound pressure gain.

It should be understood that when an element is referred to as being "disposed" on another element, it can mean that the element is directly located on the other element, or there may be an intermediate element through which the element and the other element are connected. Conversely, when an element is referred to as being "directly disposed on another element" or "directly disposed to another element", it can be understood that it is clearly defined that there are no intermediate elements.

In addition, the terms "first", "second", and "third" are only used to distinguish one element, component, region, layer, or part from another element, component, region, layer, or part, rather than to indicate a necessary order of precedence. In addition, relative terms such as "lower" and "upper" may be used herein to describe the relationship between one element and another element, and it should be understood that the relative terms are intended to include different orientations of the device in addition to the orientation shown in the figure. For example, if a device in an accompanying figure is flipped, the element described as being on the "lower" side of the other elements will be oriented on the "upper" side of the other elements. This only indicates a relative orientation relationship, not an absolute orientation relationship.

FIG. 1 is an exploded view of a multilayer piezoelectric device. FIG. 2 is an enlarged partial cross-sectional view of a multilayer piezoelectric device. FIG. 3 is a partial cross-sectional view of a multilayer piezoelectric device. According to the embodiments shown in FIG. 1 to FIG. 3 , a multilayer piezoelectric device 1 includes a semiconductor substrate 10, a multilayer piezoelectric structure 20, a first connecting electrode 40, and a second connecting electrode 50. The multilayer piezoelectric structure 20 is located on the semiconductor substrate 10 and includes a plurality of piezoelectric multilayer films 30. Each piezoelectric stacked layer film 30 is stacked in sequence, and each piezoelectric stacked layer film 30 includes, from bottom to top, a first electrode layer 31, a first piezoelectric layer 33, a second electrode layer 35, and a second piezoelectric layer 37. In order to more clearly present the connection relationship to be emphasized, some elements are omitted in FIG. 2 and FIG. 3.

The first electrode layer 31 includes a first electrode circuit pattern 311 and a first connection pattern 313, and the first connection pattern 313 is connected to the first electrode circuit pattern 311. In other words, the first electrode circuit pattern 311 and the first connection pattern 313 are jointly produced in the development and etching stages. The first piezoelectric layer 33 covers the first electrode layer 31. The second electrode layer 35 is located on the first piezoelectric layer 33 and includes a second electrode pattern 351 and a second connection pattern 353, and the second connection pattern 353 is connected to the second electrode pattern 351. The second piezoelectric layer 37 covers the second electrode layer 35. Here, the first piezoelectric layer 33 and the second piezoelectric layer 37 block electrical conduction between the first electrode layer 31 and the second electrode layer 35. The materials generally used are selected from lead zirconate titanate (Pb(ZrTi)O ₃ , PZT), barium titanate (BaTiO ₃ ), lead titanate (PbTiO ₃ ) and aluminum nitride (AlN).

The first electrode layer 31 of the bottommost piezoelectric layer film 30 is located on the semiconductor substrate 10, and the first electrode layer 31 of the remaining piezoelectric layer films 30 is located on the second piezoelectric layer 37 of the bottom piezoelectric layer film 30. Here, the vertical projections of the first connection patterns 313 in the piezoelectric layer film 30 overlap each other, and the vertical projections of the second connection patterns 353 overlap each other, and the vertical projections of the first connection patterns 313 and the second connection patterns 353 do not overlap at all.

The laminated piezoelectric structure 20 includes a first opening 21 and a second opening 23, which penetrate from the top to the bottom of the laminated piezoelectric structure 20. The first opening 21 and the second opening 23 respectively expose a portion of the first connection pattern 313 of each piezoelectric laminate film 30 and a portion of the second connection pattern 353 of each piezoelectric laminate film 30. The first connection electrode 40 is located in the first opening 21, connected to the first connection pattern 313 of each first electrode layer 31, so as to connect each first electrode layer 31 in parallel. The second connection electrode 50 is located in the second opening 23, connected to the second connection pattern 353 of each second electrode layer 35, so as to connect each second electrode layer 35 in parallel. In other words, the first connection pattern 313 and the second connection pattern 353 are led to different sides, and the first connection patterns 313 are connected to each other through the first connection electrode 40 and the second connection patterns 353 are connected to each other through the second connection electrode 50 by drilling technology. In this way, it is not necessary to reserve an electrode opening in each laminated piezoelectric structure 20, and the effect of multi-layer stacking can be achieved.

Based on the structure of the above embodiment, the area of each piezoelectric layer film 30 is the same. In this way, the mask design in the manufacturing can be more convenient. In addition, in some embodiments, the number of piezoelectric layer films 30 is greater than five, preferably, the number of piezoelectric layer films 30 is greater than eight. In this way, a better sound pressure gain can be achieved for manufacturing a micro-electromechanical piezoelectric loudspeaker.

1 and 2 , the semiconductor substrate 10 is a silicon substrate. Furthermore, for lattice matching, a silicon dioxide layer 11 is further included between the semiconductor substrate 10 and the laminated piezoelectric structure 20.

In some embodiments, the first electrode layer 31 and the second electrode layer 35 are platinum, copper, or aluminum. Furthermore, in order to achieve lattice matching and reduce defects, a titanium layer 60 is further included between the first electrode layer 31 of the bottom of the piezoelectric stack film 30 and the semiconductor substrate 10.

Figure 4 is a frequency comparison diagram of the MEMS piezoelectric speaker using multilayer piezoelectric elements and the traditional MEMS piezoelectric speaker in a free sound field. Figure 5 is a frequency comparison diagram of the MEMS piezoelectric speaker using multilayer piezoelectric elements and the traditional MEMS piezoelectric speaker in a pressure sound field.

Here, the experimental example is a structure of stacking five layers of piezoelectric multilayer films 30 as a micro-electromechanical speaker as shown in FIG. 1 of the present case. The comparative example is a conventional micro-electromechanical speaker. FIG. 4 and FIG. 5 are actual measurements in a frequency range of 100 Hz to 20 kHz under a free sound field and a pressure sound field. The driving voltage applied to the experimental example is an AC voltage of 5 Vrms, while the voltage applied to the comparative force is an AC voltage of 15 Vrms. Here, it is expected that the contribution of the parallel connection of the electrodes of the multilayer structure in the micro-electromechanical piezoelectric speaker using the multilayer piezoelectric element can provide a lower driving voltage.

Here, in the wave spectrum diagram, it can be seen that the MEMS piezoelectric speaker using multilayer piezoelectric elements has better high-frequency performance. At the same time, whether in a free sound field or a pressure sound field, the MEMS piezoelectric speaker using multilayer piezoelectric elements has better acoustic performance. The multilayer structure can reach a maximum of 69.9 dB in a free sound field, while the comparison example can only reach 38.7 dB, and the sound pressure gain is about 30 times. In addition, the MEMS piezoelectric speaker using multilayer piezoelectric elements can reach a maximum of 91.5 dB in a pressure sound field, and the single-layer structure can reach a maximum of 72.6 dB, and the sound pressure gain is about 10 times.

In summary, in some embodiments, the first connection pattern 313 and the second connection pattern 353 are designed to be on different sides, and the first connection patterns 313 are connected to each other through the first connection electrode 40 and the second connection patterns 353 are connected to each other through the second connection electrode 50 by drilling technology. In this way, it is not necessary to reserve an electrode opening when each layer is stacked, and the effect of multi-layer stacking can be achieved, and when used as a micro-electromechanical speaker, it can have a better performance in sound pressure gain.

Although the technical contents of the present disclosure have been disclosed as above with the preferred embodiments, they are not used to limit the present disclosure. Any slight changes and modifications made by anyone skilled in the art without departing from the spirit of the present disclosure should be included in the scope of the present disclosure. Therefore, the protection scope of the present disclosure shall be subject to the definition of the attached patent application scope.

1: Laminated piezoelectric element 10: Semiconductor substrate 11: Silicon dioxide layer 20: Laminated piezoelectric structure 21: First opening 23: Second opening 30: Piezoelectric laminate film 31: First electrode layer 311: First electrode circuit pattern 313: First connection pattern 33: First piezoelectric layer 35: Second electrode layer 351: Second electrode pattern 353: Second connection pattern 37: Second piezoelectric layer 40: First connection electrode 50: Second connection electrode 60: Titanium layer

Figure 1 is an exploded view of a multilayer piezoelectric component. Figure 2 is an enlarged partial cross-sectional view of a multilayer piezoelectric component. Figure 3 is a partial cross-sectional view of a multilayer piezoelectric component. Figure 4 is a frequency comparison diagram of a MEMS piezoelectric speaker using a multilayer piezoelectric component and a conventional MEMS piezoelectric speaker in a free sound field. Figure 5 is a frequency comparison diagram of a MEMS piezoelectric speaker using a multilayer piezoelectric component and a conventional MEMS piezoelectric speaker in a pressure sound field.

1: Multilayer piezoelectric element

10: Semiconductor substrate

11:Silicon dioxide layer

20: Laminated piezoelectric structure

21: First opening

23: Second opening

30: Piezoelectric laminate film

31: First electrode layer

311: First electrode circuit pattern

313: First connection pattern

33: First piezoelectric layer

35: Second electrode layer

351: Second electrode pattern

353: Second connection pattern

37: Second piezoelectric layer

40: First connecting electrode

50: Second connecting electrode

60: Titanium layer

Claims (10)

A laminated piezoelectric element comprises: A semiconductor substrate; A laminated piezoelectric structure, located on the semiconductor substrate, comprising a plurality of piezoelectric laminated films, each of which is stacked in sequence, and each of which comprises, from bottom to top, the following: A first electrode layer, comprising a first electrode circuit pattern and a first connection pattern, wherein the first connection pattern is connected to the first electrode circuit pattern; A first piezoelectric layer, covering the first electrode layer; A second electrode layer, located on the first piezoelectric layer, comprising a second electrode pattern and a second connection pattern, wherein the second connection pattern is connected to the second electrode pattern; and A second piezoelectric layer, covering the second electrode layer, The first electrode layer of the bottom one of the piezoelectric stacked films is located on the semiconductor substrate, and the first electrode layers of the remaining piezoelectric stacked films are located on the second piezoelectric layer. The vertical projections of the first connection patterns of the piezoelectric stacked films overlap with each other, and the vertical projections of the second connection patterns of the piezoelectric stacked films overlap with each other, and the vertical projections of the first connection pattern and the second connection pattern do not overlap at all. The stacked piezoelectric structure includes a first opening and a second opening, and the first opening and the second opening respectively expose a portion of the first connection pattern of each piezoelectric stacked film and a portion of the second connection pattern of each piezoelectric stacked film; A first connecting electrode, located in the first opening, connected to each of the first electrode layers, connecting each of the first electrode layers in parallel; and A second connecting electrode, located in the second opening, connected to each of the second electrode layers, connecting each of the second electrode layers in parallel. A multilayer piezoelectric device as described in claim 1, wherein the areas of the piezoelectric multilayer films are the same. A multilayer piezoelectric device as described in claim 1, wherein the number of the piezoelectric multilayer films is greater than five. A multilayer piezoelectric device as described in claim 3, wherein the number of the piezoelectric multilayer films is greater than eight. The multilayer piezoelectric element as claimed in claim 1, wherein the first piezoelectric layer and the second piezoelectric layer are selected from the group consisting of lead zirconate titanate (Pb(ZrTi)O ₃ , PZT), barium titanate (BaTiO ₃ ), lead titanate (PbTiO ₃ ) and aluminum nitride (AlN). A multilayer piezoelectric device as described in claim 1, wherein the semiconductor substrate is a silicon substrate. The multilayer piezoelectric device as described in claim 6, wherein a silicon dioxide layer is further included between the silicon substrate and the multilayer piezoelectric structure. The multilayer piezoelectric device as described in claim 6, wherein the first electrode layer and the second electrode layer are selected from the group consisting of platinum, copper, and aluminum. The multilayer piezoelectric device as described in claim 8 further comprises a titanium (Ti) layer between the first electrode layer of the bottommost one of the piezoelectric multilayer films and the semiconductor substrate. A micro-electromechanical piezoelectric speaker comprises the multilayer piezoelectric element as described in any one of claims 1 to 9.

Images